The paper deals with the modifying role of in-group identification with respect to the ability of ideologi-cal orientations to explain political preferences. Drawing on the social identity theory, it is hypothesized that political expression of ideological orientations is dependent on relevant group identifications. The influence of ethnocentrism, post-materialism and religiosity on political party preferences is examined for those who express strong and weak national identification, separately. The outlined problems are ex-amined using the Dutch Parliamentary Election Studies (DPES) data. The results show that in-group identification affects the political expression of ideology.